Re: [v2,1/1] dmaengine: dw-axi-dmac: Support src_maxburst and dst_maxburst

[Vinod Koul <vkoul@kernel.org>]

On 13-09-23, 19:04, Tan En De wrote:
> Current implementation has hardcoded CHx_CTL.SRC_MSIZE and
> CHx_CTL.DST_MSIZE with a constant, namely DWAXIDMAC_BURST_TRANS_LEN_4.
> 
> However, to support hardware with different source/destination burst
> transaction length, the aforementioned values shall be configurable
> based on dma_slave_config set by client driver.

Are client drivers setting this today, will there be regression if not
set?

> 
> So, this commit is to allow client driver to configure
> - CHx_CTL.SRC_MSIZE via dma_slave_config.src_maxburst
> - CHx_CTL.DST_MSIZE via dma_slave_config.dst_maxburst
> 
> Signed-off-by: Tan En De <ende.tan@starfivetech.com>
> ---
> v1 -> v2:
> - Fixed typo (replaced `return -EINVAL` with `goto err_desc_get` in dma_chan_prep_dma_memcpy()).
> ---
>  .../dma/dw-axi-dmac/dw-axi-dmac-platform.c    | 38 +++++++++++++++----
>  drivers/dma/dw-axi-dmac/dw-axi-dmac.h         |  3 +-
>  2 files changed, 33 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> index dd02f84e404d..f234097dffb9 100644
> --- a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> +++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> @@ -610,7 +610,7 @@ static int dw_axi_dma_set_hw_desc(struct axi_dma_chan *chan,
>  	size_t axi_block_ts;
>  	size_t block_ts;
>  	u32 ctllo, ctlhi;
> -	u32 burst_len;
> +	u32 burst_len, src_burst_trans_len, dst_burst_trans_len;
>  
>  	axi_block_ts = chan->chip->dw->hdata->block_size[chan->id];
>  
> @@ -674,8 +674,20 @@ static int dw_axi_dma_set_hw_desc(struct axi_dma_chan *chan,
>  
>  	hw_desc->lli->block_ts_lo = cpu_to_le32(block_ts - 1);
>  
> -	ctllo |= DWAXIDMAC_BURST_TRANS_LEN_4 << CH_CTL_L_DST_MSIZE_POS |
> -		 DWAXIDMAC_BURST_TRANS_LEN_4 << CH_CTL_L_SRC_MSIZE_POS;
> +	dst_burst_trans_len = chan->config.dst_maxburst ?
> +				__ffs(chan->config.dst_maxburst) - 1 :
> +				DWAXIDMAC_BURST_TRANS_LEN_4;
> +	if (dst_burst_trans_len > DWAXIDMAC_BURST_TRANS_LEN_MAX)
> +		return -EINVAL;
> +	ctllo |= dst_burst_trans_len << CH_CTL_L_DST_MSIZE_POS;
> +
> +	src_burst_trans_len = chan->config.src_maxburst ?
> +				__ffs(chan->config.src_maxburst) - 1 :
> +				DWAXIDMAC_BURST_TRANS_LEN_4;
> +	if (src_burst_trans_len > DWAXIDMAC_BURST_TRANS_LEN_MAX)
> +		return -EINVAL;
> +	ctllo |= src_burst_trans_len << CH_CTL_L_SRC_MSIZE_POS;
> +
>  	hw_desc->lli->ctl_lo = cpu_to_le32(ctllo);
>  
>  	set_desc_src_master(hw_desc);
> @@ -878,7 +890,7 @@ dma_chan_prep_dma_memcpy(struct dma_chan *dchan, dma_addr_t dst_adr,
>  	size_t block_ts, max_block_ts, xfer_len;
>  	struct axi_dma_hw_desc *hw_desc = NULL;
>  	struct axi_dma_desc *desc = NULL;
> -	u32 xfer_width, reg, num;
> +	u32 xfer_width, reg, num, src_burst_trans_len, dst_burst_trans_len;
>  	u64 llp = 0;
>  	u8 lms = 0; /* Select AXI0 master for LLI fetching */
>  
> @@ -936,9 +948,21 @@ dma_chan_prep_dma_memcpy(struct dma_chan *dchan, dma_addr_t dst_adr,
>  		}
>  		hw_desc->lli->ctl_hi = cpu_to_le32(reg);
>  
> -		reg = (DWAXIDMAC_BURST_TRANS_LEN_4 << CH_CTL_L_DST_MSIZE_POS |
> -		       DWAXIDMAC_BURST_TRANS_LEN_4 << CH_CTL_L_SRC_MSIZE_POS |
> -		       xfer_width << CH_CTL_L_DST_WIDTH_POS |
> +		dst_burst_trans_len = chan->config.dst_maxburst ?
> +					__ffs(chan->config.dst_maxburst) - 1 :
> +					DWAXIDMAC_BURST_TRANS_LEN_4;
> +		if (dst_burst_trans_len > DWAXIDMAC_BURST_TRANS_LEN_MAX)
> +			goto err_desc_get;
> +		reg |= dst_burst_trans_len << CH_CTL_L_DST_MSIZE_POS;
> +
> +		src_burst_trans_len = chan->config.src_maxburst ?
> +					__ffs(chan->config.src_maxburst) - 1 :
> +					DWAXIDMAC_BURST_TRANS_LEN_4;
> +		if (src_burst_trans_len > DWAXIDMAC_BURST_TRANS_LEN_MAX)
> +			goto err_desc_get;
> +		reg |= src_burst_trans_len << CH_CTL_L_SRC_MSIZE_POS;

this is wrong, mempcy should never use slave config value. These values
are for peripheral and not meant for mem-mem transfers

You should try max throughput by aligning the txn to bus width available
on this system

> +
> +		reg = (xfer_width << CH_CTL_L_DST_WIDTH_POS |
>  		       xfer_width << CH_CTL_L_SRC_WIDTH_POS |
>  		       DWAXIDMAC_CH_CTL_L_INC << CH_CTL_L_DST_INC_POS |
>  		       DWAXIDMAC_CH_CTL_L_INC << CH_CTL_L_SRC_INC_POS);
> diff --git a/drivers/dma/dw-axi-dmac/dw-axi-dmac.h b/drivers/dma/dw-axi-dmac/dw-axi-dmac.h
> index eb267cb24f67..877bff395740 100644
> --- a/drivers/dma/dw-axi-dmac/dw-axi-dmac.h
> +++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac.h
> @@ -265,7 +265,8 @@ enum {
>  	DWAXIDMAC_BURST_TRANS_LEN_128,
>  	DWAXIDMAC_BURST_TRANS_LEN_256,
>  	DWAXIDMAC_BURST_TRANS_LEN_512,
> -	DWAXIDMAC_BURST_TRANS_LEN_1024
> +	DWAXIDMAC_BURST_TRANS_LEN_1024,
> +	DWAXIDMAC_BURST_TRANS_LEN_MAX  = DWAXIDMAC_BURST_TRANS_LEN_1024
>  };
>  
>  #define CH_CTL_L_DST_WIDTH_POS		11
> 
> base-commit: 3669558bdf354cd352be955ef2764cde6a9bf5ec
> -- 
> 2.34.1

-- 
~Vinod